Alloy Composition

ABSTRACT

An alloy composition comprises 73.0 to 74.5 wt % of Ag and 25.5-27.0 wt % of Sn; 30.0-67.5 wt % of Ag and 32.5-70.0 wt % of In; or 29.0-60.0 wt % of Ag, 19.0-35.0 wt % of Sn and 20.0-35.2 wt % of In, wherein the particle diameter of Ag is between 10 nm to 200 μm. The alloy composition in the present invention has characters of low melting point, low hardness and high ductility. On the other hand, after a heat treatment, the alloy composition is tended to be high in melting point, hardness, strength, stability and conductivity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an alloy composition, particularly toan alloy composition with low melting point, low hardness, and highductility.

2. Description of the Related Art

The development of Micro Electro-Mechanical System (MEMS) derives fromthe combination of semiconductor processes and Precision Machinerytechnologies, which leads all kinds of industrial products becomelighter, slimmer, and shorter, multi-functional, more intelligent, andenergy saving, for example some products for medical surgery,biotechnology, and informational technology are involved. In accord with(To accomplish the trend of those) the requirements of industrialproducts, the MEMS producers and researchers are tended to develop newmicro machining technologies. Germany for example, as the mostrepresentative European country developed micro machining technology,also being one of the earliest countries to developed lithogrophyelectroforming micro molding (also called Lithographie GaVanoformungAbformung, LIGA), enthusiastically dedicates to the researches ofsilicon micromachining and micromachining technologies. The developmentsof micromachining of semiconductor processes in the USA are mainly basedon Si. By contrast, technique of micromachining that developed fromJapan is much more different. The Japanese micromachining techniques aredeveloped from traditional mechanic technologies, taking advantage overJapanese's leading electronically technique to develop variousmicromachining products.

Other micromachining technologies, such as a hot embossing process, arederived from LIGA technology. Using the hot embossing process on highpolymer membranes to produce products with micro-feature design is animportant and potential technology to processing technologies.Accordingly, the development of hot embossing process is an urge need toresearchers to approach because the hot press molding can be used bythermo plasticity or thermosetting on high polymer. The key process toproduce a product with patterns or micro structures is to put highpolymer substrate, such as polycarbonate or polymethyl methacrylateacrylic, in a molding machine and then heat the substrate to atemperature higher than its glass transition temperature (Tg). Besides,a mold with patens or micro structures made by a micro-CNC or by LIGAtechnology is prepared to press the high polymer substrate in a vacuumchamber, so as to completely print each paten and microstructure of themold onto the high polymer substrate for embossing. After the substrateis kept at the temperature for a certain time, the mold is cooled to atemperature lower than the glass transition temperature, and then thehigh polymer substrate is separated from the mold to make the productswith patens and microstructures.

The micro machining technology is one of few options of the processingtechnologies that could be used on MEMS mass production. However, themicromachining technology can only be used on producing plastic microdevices. Plastic micro devices are widely used on an application market,however, metal can be more suitable on practice because of therequirements of the applied products such as its stabilities, heatconduction, electrically conductivity and so on.

Unfortunately, hot plasticity feature on metals are not as good as thaton plastics, therefore hot press molding could not be appropriateapplied on metals. Nowadays, most metal micro devices are molded by LIGAtechnology. As an example, soften compositions that are wildly used onprior application markets are eutectic alloys of solder, and are mainlyselected from a group of Sn, Pb, Ag, Cu, Ni and other trace elements,wherein Sn is used as the principal component. For example, eutecticalloy of solder are alloyed with Sn and 37 wt % of Pb, Sn and 0.9 wt %of Cu, Sn and 3.5 wt % of Ag, Sn, 3.5 wt % of Ag and 0.5 wt % of Cu.However, the mechanical properties of the solder alloy that mentionedabove can not be efficiently enhanced, even being processed by micro hotpressing and thermal reaction because the solder alloys are made by highratio of Sn, and by melting with high temperature. Therefore it isnecessary to develop a metal composition which can be mold by hotpressing, also have the characteristics of high hardness, high meltingpoint, and high strength after a heat treatment.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide an alloy compositionwhich can overcome the disadvantages of prior art described above.

Another objective of the present invention is to provide an alloycomposition with low melting point, low hardness, and high ductilitywhich can perform high melting point, high hardness, high strength, highstability and great conductivity after a heat treatment, such as a hotembossing process or aging.

The present invention provides an alloy composition comprising 72.0-74.5wt % of Ag and 25.5-27.0 wt % of Sn, wherein the particle diameter of Agis between 10 nm to 200 μm.

The present invention provides an alloy composition comprising 29.0-67.5wt % of Ag and 31.5-70.0 wt % of In, wherein the particle diameter of Agis between 10 nm to 200 μm.

The present invention provides an alloy composition comprising 29.0-60.0wt % of Ag, 19.0-35.0 wt % of Sn, and 20.0-35.2 wt % of In, wherein theparticle diameter of Ag is between 10 nm to 200 μm.

The present invention will become clearer in light of the followingdetailed description of illustrative embodiments of this inventiondescribed in connection with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may best be more fully understood by reading thefollowing detailed description and examples with references made to theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating a process of a composition of specialalloy;

FIG. 2 is a diagram illustrating a process of a hot embossing processfor the alloy composition;

FIG. 3 is a diagram of a molding gland to the hot embossing process forthe alloy composition;

FIG. 4 is a diagram of a metal micro device after the hot embossingprocess; and

FIG. 5 is the metal micro device with a micro-channel.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an alloy composition which comprises amixture of soft metal and Ag powder.

The soft metal has characters of low melting point, low hardness, andhigh ductility, which can be selected form a group of tin (Sn), indium(In), indium-tin alloy, tin-based alloy, indium-based alloy andindium-tin-based alloy. As described above, the tin-based alloy can bean alloy comprising Sn and 0.9 wt % of copper (Cu); Sn and 3.5 wt % ofAg; Sn and 0.7 wt % of nickel (Ni); Sn, 3.5 wt % of Ag, and 0.5 wt % ofCu; Sn, 3.0 wt % of Ag, and 0.9 wt % of Cu; Sn and 9.0 wt % of zinc (Zn)alloy or Sn and “x” wt % of aluminum (Al) alloy. The indium-based alloycan be an alloy comprising In and 0.9 wt % of Cu; In and 1.2 wt % of Ag;In and 1.2 wt % of Ni; or In and “x” wt % of Zn. In the presentinvention, the alloy composition shows the characters of soft metalduring a mixing process and before a heat treatment, including lowmelting point, low hardness, and high ductility.

The soft metal of the alloy composition also can be a tin-based solderalloy or an indium-based solder alloy to reduce the consumption of theAg powder, also to improve the mechanical properties of the alloycomposition. The Ag powder in the alloy composition of the presentinvention is ground in advance with a particle diameter between 10 nm to200 μm, which is uniformly distributed over the texture of soft metal.

After the heat treatment, the soft metal and the Ag powder in the alloycomposition are re-constructed into a new structural texture, which makethe alloy composition tend to has characters of high melting point, highhardness, high strength, high stability and great conductivity.Furthermore, the alloy composition also can be mixed with 0.01-2.0 wt %of Cu, 0.01-2.0 wt % of Ni, or 0.01-3.0 wt % of germanium (Ge) forpromoting the thermal conductivity, enhancing the corrosion resistanceand mechanical properties, or for decreasing the melting point andwettability before the heat treatment respectively.

In fact, it is impossible to mix the pure Ag powder and the soft metalwithout any other substances, like Cu, Ni, gold (Au) and Zn, andaccordingly the properties of the alloy composition might be changed dueto the contamination of Cu, Ni, gold (Au) and Zn in the Ag powder andthe soft metal. On the other hand, a particular amount of Cu powder orNi powder could also be blended into the alloy composition if necessary.

Referring to FIG. 1, it illustrates a preferable production diagram ofthe alloy composition in the present invention, and it is to beunderstood that the process of the alloy composition is not limitedthereto.

As show in FIG. 1, the alloy composition in the present invention isproduced by rolling-mix method. Firstly, soften metal, such as Sn, In,or In—Sn alloy, is pressed into a plurality of metal foils 2 by arolling equipment 1. Secondary, the Ag powder 3 with the diameter ofeach particle thereof between 10 nm and 200 μm is evenly arrangedbetween the metal foils 2, and then the metal foils 2 with the Ag powder3 is pressed by the rolling equipment 1 again to obtain a metal foil 2′.Finally, the metal foil 2′ is repeatedly folded and rolling pressed bythe rolling equipment 1, so that the Ag powder 3 can be completely andevenly mixed into the metal foil 2 to obtain a alloy composition 4.Moreover, Cu metal powder and Ni metal power can be individually mixedup with the Ag metal powder 3 to obtain Ag—Cu metal powder, Ag—Ni metalpowder or Ag—Cu—Ni meta for spreading on the metal foil 2 following bythe process of rolling pressing by the rolling equipment 1, folding androlling pressing again as described above. Finally after repeatedlyfolding and rolling pressing, the alloy composition 4 with a pluralityratio of Cu metal powder or Ni metal powder can be obtained thereby.

Referring to FIGS. 2, 3 and 4 illustrate a hot embossing process of thealloy composition. The alloy composition in the present invention showsthe characteristics of low malting point, high ductility, and softbefore the heat treatment, therefore the alloy composition is sufficientto be processed by hot embossing to manufacture into metal microdevices. For example, the alloy composition 4 in the present inventionis heated by a heating equipment 5, with a preferable heatingtemperature approaching to the malting point (Tm) of the alloycomposition 4, such as Tm−100° C.<T<Tm+100° C. Then, a mold 6 iscovering pressed on the alloy composition 4 under a circumstance of avacuum chamber or standard atmospheric pressure in order to transfer apattern 61 from the mold 6 to the alloy composition 4. As a result, amicro structure 41 corresponded with the pattern 61 is form on thesurface of the special composition 4. As following, the alloycomposition 4 and the mold 6 are contacted and kept at a temperature fora period in order to make the metal in the alloy composition 4undergoing the process of “isothermal solidification”, thereby anintermetallic compounds with characteristic of high malting point andhigh hardness will be produced. Finally, to cool down and remove themold 6, a micro metal device manufactured from the alloy composition 4are obtained, wherein some microstructures, like micro-indentation ormicro-channel 41 may be shaped on the surface of the alloy composition4.

In FIG. 5 illustrates the alloy composition with micro structure 41 ofmicrochannel on the surface. The alloy composition 4 which had beenfinished the thermal reaction and had become a micro metal device,consists characteristics of high melting point, high hardness, highstrength, high stability and great conductivity, therefore the alloycomposition could be applied on Micro Electro-Mechanical System (MEMS).In summary, the alloy composition 4 in the present invention, havecharacteristics of low malting point, high ductility, and soft beforethe hot embossing process, therefore the alloy composition can beapplied on the hot embossing process for overcoming the weakness ofnormal metal in hot embossing process, like high malting point and poorplasticity. On the other hand, after the hot embossing process, thealloy composition 4 in the present invention may become a good micrometal device with high hardness, high malting point, high strength, highstability and great conductivity that can expand the application of themicro metal device. On the other hand, the application of the alloycomposition in the present invention is not restricted to hot pressmolding. Take another hot embossing process for example. An initialalloy composition (before heat treatment) of present invention hascharacteristics of low malting point, high ductility, and soft.Therefore the alloy composition can be applied on the process ofmicroelectronics packaging process, such as assemble a micro-circuitcontacts between chips or assemble a connect between circuit boardcontaining and a chip. However, after a thermal reaction of reflow,solder chips welding together. From a prior art knows that electronicproducts will be heated after overcurrent, therefore a weld which ismade by the alloy composition will become

the material that consist the characteristics of high melting point,high hardness, high strength, high stability and great conductivitybecause the alloy composition accomplished the reaction of the hotembossing that induced by overcurrent.

In four preferable examples described as following summarize the alloycomposition with different metallic ratio in the present invention.

In the example 1, the alloy composition, with Sn as the soft metal,comprises 72.0-74.5 wt % of Ag and 24.5-27.0 wt % of Sn, particular for74 wt % of Ag and 26 wt % of Sn. The alloy composition in the example 1is heated under a temperature between 230° C. and 400° C., morepreferable at 260° C. for hot embossing process. After the heattreatment, a large number of Ag₃Sn intermetrallic compound or anorganizational structure of Ag₃Sn intermetrallic compound are producedin the internal structure of the metal micro-component which couldgreatly increased the melting point and hardness of the metalmicro-component.

In the example 2, the alloy composition; with In as the soft metal,comprises 29.0-67.5 wt % of Ag and 31.5-70.0 wt % of In, particular for29-32 wt % of Ag and 66.5-70 wt % of In and most preferable for 31.7 wt% of Ag, 68.1 wt % of In and 0.2 wt % of Cu. The alloy composition inthe example 2 is heated under a temperature between 100° C. and 160° C.,more preferable at 156° C. for hot embossing process. After the heattreatment, a large number of AgIn₂ intermetrallic compound or anorganizational structure of AgIn₂ intermetrallic compound are producedin the internal structure of the metal micro-component which couldgreatly increased the melting point and hardness of the metalmicro-component.

In the example 3, the alloy composition, with In selected as the softmetal, comprises 29.0-67.5 wt % of Ag and 31.5-70.0 wt % of In,particular for 67-67.5 wt % of Ag and 31.5-35 wt % of In and mostpreferable for 66.7 wt % of Ag, 32 wt % of In and 0.3 wt % of Ni. Thealloy composition in the example 3 is heated under a temperature between150° C. and 250° C., more preferable at 220° C. for hot embossingprocess. After the heat treatment, a large number of AgIn₂intermetrallic compound or an organizational structure of AgIn₂intermetrallic compound are produced in the internal structure of themetal micro-component.

In the example 4, the alloy composition, with indium-tin alloy selectedas the soft metal, comprises 29.0-60 wt % of Ag, 19-35 wt % of Sn and20-35.2 wt % of In, particular for 35 wt % of Ag, 30 wt % of Sn and 35wt % of In. The alloy composition in the example 4 is heated under atemperature between 150° C. and 250° C., more preferable at 200° C. forhot embossing process. After the heat treatment, a large number ofintermetrallic compounds, Ag₃Sn, Ag₂In, AgIn₂ and AgInSn₂ for example,are produced in the internal structure of the metal micro-component.

Thus, to further adjust the ratio between Ag and the soft metal of thealloy composition, the operated temperature of the micro-compressionmolding can be differentially set in accord with the need of use.

As described above, mixing the Ag powder with the soft metal can obtainthe alloy composition in the present invention, with characters of lowmelting point, low hardness and high ductility which can be used on thehot embossing process. After the heat treatment, the hot embossingprocess, the intermetrallic compound of the alloy composition aretransformed and tented to show high melting point, high hardness, highstrength, high stability and great conductivity to improve the featureof the alloy composition.

The alloy composition in the present invention can also be used as asolder for the surface mount technology (SMT) of electrical device.Therefore the electrical device can be welded on a board (such as amotherboard or a mobile phone board), and 3D packaging has been used forapplication. The alloy composition of the present invention can sustaina overheating that occurred to the process of 3D packaging. However, itis need to be understood that an example that mentioned above is one ofthe applications of the alloy composition in the present invention.

The alloy composition in present invention, with characters of lowmelting point, low hardness, and high ductility, can be applied to hotembossing process. The alloy composition would transfer to anintermetallic compounds, which could effectively enhance theperformances of the alloy composition after a heat treatment (such ashot embossing process), including high melting point, high hardness,high strength, high stability and great conductivity.

Thus since the invention disclosed herein may be embodied in otherspecific forms without departing from the spirit or generalcharacteristics thereof, some of which forms have been indicated, theembodiments described herein are to be considered in all respectsillustrative and not restrictive. The scope of the invention is to beindicated by the appended claims, rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

1. An alloy composition comprising: 72.0-74.5 wt % of Ag and 24.5-27.0wt % of Sn, wherein the particle diameter of Ag is from 10 nm to 200 μm.2. The alloy composition as claimed in claim 1 further comprising0.01-2.0 wt % of Cu.
 3. The alloy composition as claimed in claim 1further comprising 0.01-2.0 wt % of Ni.
 4. The alloy composition asclaimed in claim 1, wherein a structural texture of the alloycomposition as Ag₃Sn intermetrallic compound is formed after a thermalreaction at 230° C. to 400° C.
 5. An alloy composition comprising:29.0-67.5 wt % of Ag and 31.5-70.0 wt % of In, wherein the particlediameter of Ag is from 10 nm to 200 μm.
 6. The alloy composition asclaimed in claim 5, wherein the Ag is 29.0-32.0 wt % and the In is66.5-70.0 wt %.
 7. The alloy composition as claimed in claim 6, whereina structural texture of the alloy composition transforming as AgIn₂intermetrallic compound is formed after a thermal reaction at 100° C. to160° C.
 8. The alloy composition as claimed in claim 5, wherein the Agis 64.0-67.5 wt % and the In is 31.5-35.0 wt %.
 9. The alloy compositionas claimed in claim 8, wherein a structural texture of the alloycomposition as Ag₂In intermetrallic compound is formed after a thermalreaction at 150° C. to 250° C.
 10. The alloy composition as claimed inclaim 5, wherein the Ag is mixed in the In by a rolling-mix method. 11.The alloy composition as claimed in claim 5, further comprising 0.01-2.0wt % of Cu.
 12. The alloy composition as claimed in claim 5, furthercomprising 0.01-2.0 wt % of Ni.
 13. An alloy composition comprising29.0-60.0 wt % of Ag, 19.0-35.0 wt % of Sn, and 20.0-35.2 wt % of In,wherein the particle diameter of Ag between 10 nm to 200 μm.
 14. Thealloy composition as claimed in claim 13, wherein a structural textureof the alloy composition as an intermetrallic compound is formed after athermal reaction at 150° C. to 250° C.
 15. The alloy composition asclaimed in claim 13, wherein the Ag is mixed in the Sn and the In by arolling-mix method.
 16. The alloy composition as claimed in claim 13,further comprising 0.01-2.0 wt % of Cu.
 17. The alloy composition asclaimed in claim 13, further comprising 0.01-2.0 wt % of Ni.